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049a947c AN |
1 | /* |
2 | * RNG driver for TX4939 Random Number Generators (RNG) | |
3 | * | |
4 | * Copyright (C) 2009 Atsushi Nemoto <anemo@mba.ocn.ne.jp> | |
5 | * | |
6 | * This file is subject to the terms and conditions of the GNU General Public | |
7 | * License. See the file "COPYING" in the main directory of this archive | |
8 | * for more details. | |
9 | */ | |
c7c9e1c3 | 10 | #include <linux/err.h> |
049a947c AN |
11 | #include <linux/module.h> |
12 | #include <linux/kernel.h> | |
13 | #include <linux/init.h> | |
14 | #include <linux/delay.h> | |
15 | #include <linux/io.h> | |
16 | #include <linux/platform_device.h> | |
17 | #include <linux/hw_random.h> | |
5a0e3ad6 | 18 | #include <linux/gfp.h> |
049a947c AN |
19 | |
20 | #define TX4939_RNG_RCSR 0x00000000 | |
21 | #define TX4939_RNG_ROR(n) (0x00000018 + (n) * 8) | |
22 | ||
23 | #define TX4939_RNG_RCSR_INTE 0x00000008 | |
24 | #define TX4939_RNG_RCSR_RST 0x00000004 | |
25 | #define TX4939_RNG_RCSR_FIN 0x00000002 | |
26 | #define TX4939_RNG_RCSR_ST 0x00000001 | |
27 | ||
28 | struct tx4939_rng { | |
29 | struct hwrng rng; | |
30 | void __iomem *base; | |
31 | u64 databuf[3]; | |
32 | unsigned int data_avail; | |
33 | }; | |
34 | ||
35 | static void rng_io_start(void) | |
36 | { | |
37 | #ifndef CONFIG_64BIT | |
38 | /* | |
39 | * readq is reading a 64-bit register using a 64-bit load. On | |
40 | * a 32-bit kernel however interrupts or any other processor | |
41 | * exception would clobber the upper 32-bit of the processor | |
42 | * register so interrupts need to be disabled. | |
43 | */ | |
44 | local_irq_disable(); | |
45 | #endif | |
46 | } | |
47 | ||
48 | static void rng_io_end(void) | |
49 | { | |
50 | #ifndef CONFIG_64BIT | |
51 | local_irq_enable(); | |
52 | #endif | |
53 | } | |
54 | ||
55 | static u64 read_rng(void __iomem *base, unsigned int offset) | |
56 | { | |
57 | return ____raw_readq(base + offset); | |
58 | } | |
59 | ||
60 | static void write_rng(u64 val, void __iomem *base, unsigned int offset) | |
61 | { | |
62 | return ____raw_writeq(val, base + offset); | |
63 | } | |
64 | ||
65 | static int tx4939_rng_data_present(struct hwrng *rng, int wait) | |
66 | { | |
67 | struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng); | |
68 | int i; | |
69 | ||
70 | if (rngdev->data_avail) | |
71 | return rngdev->data_avail; | |
72 | for (i = 0; i < 20; i++) { | |
73 | rng_io_start(); | |
74 | if (!(read_rng(rngdev->base, TX4939_RNG_RCSR) | |
75 | & TX4939_RNG_RCSR_ST)) { | |
76 | rngdev->databuf[0] = | |
77 | read_rng(rngdev->base, TX4939_RNG_ROR(0)); | |
78 | rngdev->databuf[1] = | |
79 | read_rng(rngdev->base, TX4939_RNG_ROR(1)); | |
80 | rngdev->databuf[2] = | |
81 | read_rng(rngdev->base, TX4939_RNG_ROR(2)); | |
82 | rngdev->data_avail = | |
83 | sizeof(rngdev->databuf) / sizeof(u32); | |
84 | /* Start RNG */ | |
85 | write_rng(TX4939_RNG_RCSR_ST, | |
86 | rngdev->base, TX4939_RNG_RCSR); | |
87 | wait = 0; | |
88 | } | |
89 | rng_io_end(); | |
90 | if (!wait) | |
91 | break; | |
92 | /* 90 bus clock cycles by default for generation */ | |
93 | ndelay(90 * 5); | |
94 | } | |
95 | return rngdev->data_avail; | |
96 | } | |
97 | ||
98 | static int tx4939_rng_data_read(struct hwrng *rng, u32 *buffer) | |
99 | { | |
100 | struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng); | |
101 | ||
102 | rngdev->data_avail--; | |
103 | *buffer = *((u32 *)&rngdev->databuf + rngdev->data_avail); | |
104 | return sizeof(u32); | |
105 | } | |
106 | ||
107 | static int __init tx4939_rng_probe(struct platform_device *dev) | |
108 | { | |
109 | struct tx4939_rng *rngdev; | |
110 | struct resource *r; | |
111 | int i; | |
112 | ||
049a947c AN |
113 | rngdev = devm_kzalloc(&dev->dev, sizeof(*rngdev), GFP_KERNEL); |
114 | if (!rngdev) | |
115 | return -ENOMEM; | |
9dc48034 | 116 | r = platform_get_resource(dev, IORESOURCE_MEM, 0); |
c7c9e1c3 TR |
117 | rngdev->base = devm_ioremap_resource(&dev->dev, r); |
118 | if (IS_ERR(rngdev->base)) | |
119 | return PTR_ERR(rngdev->base); | |
049a947c AN |
120 | |
121 | rngdev->rng.name = dev_name(&dev->dev); | |
122 | rngdev->rng.data_present = tx4939_rng_data_present; | |
123 | rngdev->rng.data_read = tx4939_rng_data_read; | |
124 | ||
125 | rng_io_start(); | |
126 | /* Reset RNG */ | |
127 | write_rng(TX4939_RNG_RCSR_RST, rngdev->base, TX4939_RNG_RCSR); | |
128 | write_rng(0, rngdev->base, TX4939_RNG_RCSR); | |
129 | /* Start RNG */ | |
130 | write_rng(TX4939_RNG_RCSR_ST, rngdev->base, TX4939_RNG_RCSR); | |
131 | rng_io_end(); | |
132 | /* | |
133 | * Drop first two results. From the datasheet: | |
134 | * The quality of the random numbers generated immediately | |
135 | * after reset can be insufficient. Therefore, do not use | |
136 | * random numbers obtained from the first and second | |
137 | * generations; use the ones from the third or subsequent | |
138 | * generation. | |
139 | */ | |
140 | for (i = 0; i < 2; i++) { | |
141 | rngdev->data_avail = 0; | |
142 | if (!tx4939_rng_data_present(&rngdev->rng, 1)) | |
143 | return -EIO; | |
144 | } | |
145 | ||
146 | platform_set_drvdata(dev, rngdev); | |
147 | return hwrng_register(&rngdev->rng); | |
148 | } | |
149 | ||
150 | static int __exit tx4939_rng_remove(struct platform_device *dev) | |
151 | { | |
152 | struct tx4939_rng *rngdev = platform_get_drvdata(dev); | |
153 | ||
154 | hwrng_unregister(&rngdev->rng); | |
049a947c AN |
155 | return 0; |
156 | } | |
157 | ||
158 | static struct platform_driver tx4939_rng_driver = { | |
159 | .driver = { | |
160 | .name = "tx4939-rng", | |
049a947c AN |
161 | }, |
162 | .remove = tx4939_rng_remove, | |
163 | }; | |
164 | ||
e7c2199f | 165 | module_platform_driver_probe(tx4939_rng_driver, tx4939_rng_probe); |
049a947c AN |
166 | |
167 | MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver for TX4939"); | |
168 | MODULE_LICENSE("GPL"); |